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M5 > 5.10 fibre optics > Flashcards

5.10 fibre optics Flashcards

1
Q

what is refraction

A

Refraction is the bending of light as it passes from one transparent medium to another

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2
Q

what is reflection

A

When a beam of light strikes a smooth polished surface, regular reflection occurs.

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3
Q

fibre optics transmit signals using

A

light rather than electricity

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4
Q

a fibre optic cable is a

A

flexible filament of very clear glass capable of carrying information in the form of light

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5
Q

what can the light source be for fibre optics

A

either a light-emitting diode LED or a laser.

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6
Q

The light source is pulsed on and off, and a light-sensitive receiver on the other end of the cable converts the pulses back into the digital ones and zeros of the original signal.

A

.

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7
Q

there are five key elements of an optical fibre what are they

A
  • the core
  • the cladding
  • the coating
  • the strength member
  • the outer jacket
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8
Q

the core =

A

made of glass or plastic, provides the path for light propagation

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9
Q

the cladding =

A

surrounds the core completely and prevents light from exiting the core and being absorbed by the rest of the cable

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10
Q

the coating =

A

aka buffer, protects the core and cladding and provides strength

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11
Q

the strength member =

A

fibre is manufactured into a cable, the next layer is a material, such as Kevlar or Aramid, that provides strength to the cable and helps prevent damage due to stress

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12
Q

outer jacket =

A

the jacket is typically coloured to Ident. what optical fibre is in the cable

entire package encased in jacket, one final layer of strength and protection.

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13
Q

electromagnetic spectrum is

A

the range of wavelengths or frequencies covered by electromagnetic radiation

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14
Q

velocity of light =

A

the speed at which light passes through a given material

3 x 108 m/s or 300 000 kilometres per second (186 000 miles per second)

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15
Q

rectilinear propagation is when

A

light travelling in straight lines as long as it stays in a uniform medium

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16
Q

wavelength =

A

Fibre transmission depends on wavelength. They can be expressed as frequency – often in Gigahertz (GHz) or Terahertz (THz). The usual operating bands are 850, 1310, 1550 nm

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17
Q

Bandwidth =

A

Bandwidth refers to the amount of data you can transfer in a unit of time

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18
Q

what is an LED

A

light emitting diode is a semiconductor device that emits light when an electric current flows through it

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19
Q

LASER =

A

light amplification by stimulated emission of radiation

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20
Q

Decibel dB =

A

Performance is measured in decibels (dB). This indicates how much power the light has as it moves through the cables.

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21
Q

there are two main types of fibre :

A

single mode fibre
multi mode fibre

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22
Q

Single mode fibre optic cable is the earliest form of fibre optic cable

A

This type of cable sends a single beam of light down a single stand of glass fibre with a diameter of 8.3 to 10 microns.

Single mode fibre has a narrow core and the index of refraction between the core and the cladding changes less than it does for multimode fibre

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23
Q

what mode fibre has a higher transmission rate

A

single mode fibre

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24
Q

single mode fibre covers 50 times more distance than multimode fibre but what is the drawback

A

a higher cost £

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25
Q

Multi mode fibre has a large diameter core of 50 or 62.5 microns that allows multiple modes of light to pass through it and this means that more types of data can be transmitted.

A

.

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26
Q

Multimode fibre has lower bandwidth than SM fibre and is susceptible to modal dispersion

A

.

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27
Q

what are the two main types of MM fibre

A

Step-index
Graded-Index

28
Q

Step index MM fibre:

A

The core in a step-index fibre has a uniform refractive index throughout

29
Q

(Step-Index)
There is a sharp decrease in refractive index where

A

at the core-cladding boundary where the cladding refractive index is lower than that of the core

30
Q

The refractive index of the core in a graded-index fibre decreases as the distance to the center of the core increases.

A

This results in a much smaller change in the refractive indice at the core-cladding interface

31
Q

what colour is the primary coating on most aircraft fibre optic cables to identify them

A

Purple

32
Q

Each optical fibre strand with its buffers is

A

900 microns in diameter

33
Q

The secondary buffers of the five optical fibre strands are these five colours

A

Blue
Red
Green
Yellow
White

34
Q

The primary coating is usually

A

a 250 μm protective acrylate applied during manufacture to protect the fibres from damage and environmental factors

35
Q

secondary coating

This is an additional coating for further protection, usually around 900 μm

A

.

36
Q

the basic fibre optic system contains of

A

an encoder, a decoder, fibre connecting the two units, a light source (usually LED or laser) and couplings

37
Q

what are the biggest advantages of fibre optics over electrical wire propagation

A

The biggest advantages of fibre optic cable is undoubtedly the weight saving and bandwidth

38
Q

The fibre is made of glass, which is an insulator, making it immune to electromagnetic interference (EMI) and radio-frequency interference

A

.

39
Q

copper cables are how much slower in data transmission than fibre cable

A

31%

40
Q

Because the fibre optic signal is made of light, very little signal loss occurs during transmission so data can move at higher speeds and greater distances.

A

.

41
Q

installation costs for fibre are higher than copper because of the skill needed for terminations

A

Overall, fibre is more expensive than copper in the short run, but it may actually be less expensive in the long run.

42
Q

The other advantages of fibre optic transmission are:

A

Cables are more tolerant of mechanical and environmental abuse than comparable electrical cables.

Cables are lighter than comparable electrical cables.

The energy consumed by a copper cable during its operation is somewhat greater than 10 W; conversely, fibre optics consume less energy, i.e., around 2 W per user.

Fibre optics are difficult to be tapped compared to copper cables, which is advantageous from a security point of view. For this reason, fibre optics are currently widely used for data transmission.

43
Q

The disadvantages of fibre optic transmission are:

A

Repair and splicing require special methods.

Terminations require special care.

Laser sources can be hazardous, particularly to the eyes (corneal or retina burns) and skin due to the ultraviolet wavelengths (290 - 320 nm).

Optical and electrical converters. Limitations of fibre optics arise mainly from the need for optical or electrical conversion and the implementation and maintenance of the physical connections

44
Q

fibre is only used on the following non critical systems which are

A

Electronic Flight Bag - Electronics Unit
Electronic Flight Bag - Display Unit
In-Flight Entertainment Equipment

45
Q

Terminal connectors look similar to normal aircraft connectors except that the pins and sockets are replaced with

A

alignment pins and holes

46
Q

A fibre optic data bus operates similarly to an electrical data bus, except that it carries light instead of electricity.

A

The transmitter converts electrical signals into light pulses and sends these over the fibre optic cable to the receiver.

47
Q

Unlike copper wire, fibre optic cables cannot be soldered or crimped to make a low-resistance connection

A

.

48
Q

SC - Square Connector or Standard Connector (FIBRE OPTICS)

A

This is probably the most common type of fibre optic connector used today. It is designed to be simple to use and inexpensive to produce. The SC uses a push-pull design but uses a locking tab instead of a latch to secure the unit.

49
Q

ST - Straight Tip

A

The ST connector is a bayonet fibre optical connector. It is similar to the FC, but instead of threads, it uses the same locking mechanism as the BNC coax connectors.

50
Q

FC - Ferrule Connector or Fibre Channel

A

FC is an older fibre optic connector currently being phased out of industry standards.

51
Q

LC - Lucent Connector

A

This connector is created by Lucent Technologies. It was designed as a push-pull connector that locks in place with a latch. While being faster and easier to operate is an advantage, the main disadvantage of the LC is its about half the size of other fibre optic connectors

52
Q

Expanded Beam Fibre Optic Connector three types : A, B and C

A

in type A -plug and receptacle have ceramic contacts that touch when connected.

in B type - the connector has miniature ball lenses behind a protective window. Each lens is at the end of a fibre

Type C - connectors are like type B connectors, but the push-pull version.

53
Q

Colour Bands

A

The coupling nut on the plug barrel has a yellow band. The receptacle barrel has a red and yellow band. When the red band on the receptacle is at least 50 percent covered by the coupling nut, this shows a correct connection

54
Q

what must happen before examining the connector face or the ceramic contacts

A

the cable must be disconnected from the equipment at both ends, or the equipment must be switched off. The light from the optical fibre that attaches to the avionic equipment can be invisible and intense exposure can damage the retina of the human eye.

55
Q

the three basic principles critical to achieving an efficient fibre optic connection can be summarized as “The 3 Ps”:

A

perfect core alignment
physical contact
pristine connector interface

56
Q

generally, it is not possible to see any damage or contamination with the naked eye. Therefore, specialist equipment is required, such as

A

a Probe Microscope

57
Q

Before connecting or re-connecting fibre optic cables they MUST be cleaned. There are many ways to remove contamination. These are the different procedures for contamination removal in general use:

four ways are

A

Dry swab
Wet swab
Cartridge pen
Clean Blast © cleaning system

58
Q

Each swab must only be used once.

A

.

59
Q

The cartridge pen (otherwise known as a

A

one click

60
Q

If the connector is not installed immediately or disconnected for removal/installation of LRUs, what must happen

A

a dust cap or a plastic bag must be placed over the connector. Prior to reconnection, a visual inspection for contamination must be carried out.

61
Q

A coupler is a device with

A

multiple input or output ports, where light can travel.

62
Q

A star coupler is a device that takes in an input signal and splits it into several output signal

A

.

63
Q

Subscribers to the bus are called Remote Terminals (RT). Like any terminal, RTs can receive and transmit data. These signals can be electrical or digital (optical).

A

.

64
Q

RTs are remote monitoring devices that monitor what is going on all the time and relay information to the user e.g., flight deck or cabin crew.

A

.

65
Q

The B787 is the first Boeing commercial aircraft to carry flight-critical data over fibre optics
The B787 has 110 fibre links—more than 1 mile (1.7 km) of fibre optic cable

A

.

66
Q

The following list gives the systems containing fibre communications networks on the B787:

A

Electronic Flight Bag - Electronics Unit
Electronic Flight Bag - Display Unit
In-Flight Entertainment Equipment
Audio Control Panel
Audio Gateway Unit
Flight Recorder
Graphics Generator Module
Head-Down Display
Head-Up Display Projector
Integrated Surveillance System Processor Unit
Weather Radar Receiver/Transmitter Module
Fibre Optic Translator Module
ARINC 664 Network Remote Switch
Common Computing Resource Cabinet (58 Fibre Links)
Cabin Services System Controller
Network Interface Module

67
Q
A

M5 (12 decks)

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